Methane is a powerful greenhouse gas, and we need to measure it globally with satellite instruments. We compare measurements from two satellites with measurements from the ground in Eureka, Nunavut, Canada to assess their different strengths and weaknesses. The differences between measurements are discussed and assessed considering the details of each measurement technique and processing. Recommendations are provided for utilization of these data sets for monitoring methane in the high Arctic.
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This article presents an algorithm for cloud detection using TIR radiance spectra based on the CO2 slicing technique for improvement of GHG observation from space. The key techniques of the algorithm are channel reconstruction and their optimization for increasing sensitivity and accuracy. The analysis results using GOSAT data show general agreement with those from CALIPSO. It can be expected that this algorithm would improve the accuracy of cloud screening and gas retrievals from GOSAT data.
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Remote sensing devices known as lidars are often used to take measurements at potential wind farm sites. These instruments are however not optimized for measuring turbulence, small-scale changes in wind speed. In this manuscript, the impact of lidar configurations and atmospheric conditions on turbulence accuracy is explored. A new method was developed to correct lidar turbulence measurements and is described in detail such that other lidar users can apply it to their own instruments.
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The new spectrometer of the Munich Aerosol Cloud Scanner (specMACS) is a
multipurpose hyperspectral cloud and sky imager which is designated, but not limited, to investigations of cloud-aerosol interactions in Earth's atmosphere. This paper describes the specMACS instrument's hardware and software design and
characterizes the instrument performance. Initial measurements of cloud sides are presented which demonstrate the wide applicability of the instrument.
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This paper proposed three methods for determining the reflectivity bias of single polarization radar using dual polarization radar reflectivity and disdrometer data (i.e., the equidistance line, overlapping area, and disdrometer methods), and we evaluated for two low-pressure rainfall events that occurred over the Korean Peninsula on 25 August 2014 and 8 September 2012. Overall, the most accurate rainfall estimates were obtained using the overlapping area method to correct radar reflectivity.
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The main aim of the paper is to demonstrate an approach for the post-processing of the Dobson spectrophotometers' total ozone columns (TOCs) in order to compensate for their known stratospheric effective temperature dependency
and its resulting effect on the usage of the Dobson TOCs for satellite TOCs' validation.
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Improved line positions and intensities have been generated for the 7.6 µm spectral region of nitric acid, relying on a recent laboratory reinvestigation and comparisons of HNO3 volume mixing ratios retrieved from Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) radiances in the 11 and 7.6 µm regions. The much improved consistency of line intensities in both regions will make it possible to use them simultaneously to retrieve atmospheric HNO3.
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Knowledge on the vertical distribution of aerosols in the atmospheric is important for studying aerosol impacts on air quality and climate change. The polarization measurements in O2 A and B bands is shown here theoretically to have rich information for characterizing aerosol vertical profile over land. This paper presents a passive remote sensing technique supplementary to the existing technique to retrieve aerosol vertical distribution over land from space.
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Tiny variation in natural abundance ratios of stable isotopes of nitrogen and oxygen in nitrous oxide (N2O) can be used as a fingerprint of this trace gas that causes greenhouse effect and stratospheric ozone depletion. Toward the understanding of the global budget of N2O and its temporal change, we developed an automated sample preparation system that can be used to measure the stable isotope ratios in N2O in various air samples collected into flasks with high precision and less labor.
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During volcanic eruptions the presence of ice clouds may affect the volcanic ash signal in infrared satellite measurements. By comparison of measured infrared spectra with spectra from a radiative transfer model including both ash and ice clouds, it is shown that during the Mt Kelud February 2014 eruption, both ash and ice clouds were present simultaneously. The presence of ice clouds lowers the estimated amount of volcanic ash in the atmosphere.
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This study compared GOSAT/TANSO-FTS thermal infrared (TIR) V1 and CONTRAIL CME CO2 data in the upper troposphere and lower stratosphere. The TIR CO2 averages agreed with the CME CO2 averages within 0.1 and 0.5 % in the Southern and Northern Hemisphere. At northern low and middle latitudes, their agreements were worse in spring and summer. The negative bias there made the maximum of TIR data being lower than that of CME data, which leads to underestimating the amplitude of CO2 seasonal variation.
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This study demonstrate the detection of dimethylamine at low mixing ratios by nitrate chemical ionization mass spectrometry (CIMS). Due to simultaneously high-sensitive gas-phase measurements of DMA, sulfuric acid, and extremely low volatile organic compounds (ELVOCs), this technique can be used as a versatile tool for studying new particle formation in the atmosphere.
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We address specialities of differential optical absorption spectroscopy of scattered light in the presence of strong absorbers (like ozone), where the optical depth becomes a non-linear function of the absorber concentration. We quantify the non-linearity using higher-order terms by expanding the radiative transfer equation in a Taylor series.
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Aerosol particles are an important component of the Earth's atmosphere. Here we describe the composition and characterization of a new optical particle size spectrometer (OPSS) for aircraft-borne measurements of the aerosol particle size distribution (how many particles there are with a certain size) in the 140–1050 nm size range. The OPSS was characterized throughout concerning its measurement capabilities (response, pressure dependence, coincidence) and validated versus balloon measurement.
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Current measurement methods do not provide information about the speciation of oxidized mercury compounds in the atmosphere, leading to uncertainty about which mercury compounds exist and how oxidized mercury is formed. We have developed a gas chromatography/mass spectrometry-based system for identification of oxidized mercury compounds. We discuss the main features and performance of this system.
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Because a systematic difference between measurements of water vapor performed by space-borne observing instruments in the microwave spectral domain and their numerical modeling was recently highlighted, this work discusses and gives an overview of the various errors and uncertainties associated with each element in the comparison process. Indeed, the knowledge of absolute errors in any observation of the climate system is key, more specifically because we need to detect small changes.
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A new microwave satellite water vapour retrieval method for use in the Arctic winter has been developed that uses auxiliary information for atmospheric conditions. When compared to ground-based measurements, the new retrieval has a smaller root mean square deviation than other satellite measurement techniques and can produce high-resolution pan-Arctic water vapour column maps.
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This paper is presenting a feasibility study focused on methods of estimating the turbulence intensity based on a class of navigational messages routinely broadcast by the commercial aircraft (known as ADS-B and Mode-S). Using this kind of information could have potentially significant impact on aviation safety. Three methods have been investigated.
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The goal of CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrumented Container) is to carry out regular and detailed observations of atmospheric chemistry at 9–12 km altitude. Mercury has been measured since May 2005 during intercontinental flights between Europe and South and North America, Africa, and Asia. Here we describe the instrument modifications, the post-flight processing of the raw instrument signal, and the fractionation experiments.
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We describe an extension of a portable FTIR (Fourier transform infrafed) spectrometer dedicated to the measurement of column-averaged abundances of greenhouse gases in the atmosphere. The measurement principle is based on a spectrally resolved solar absorption observation (trace gas amounts are deduced from the strength of near-infrared absorption bands). The dual-channel set-up presented here allows co-observing CO while maintaining the highly favourable characteristics of the original device.
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Atmospheric remote sounding from space is fundamental for investigating the processes driving climate change. However, for a correct scientific interpretation of these records a documentation of their quality is required. In this context, this paper exploits the high potential of the Izaña Atmospheric Observatory, as a ground-based reference site, to perform the first comprehensive validation of the EUMETSAT atmospheric trace gas products O3, CH4, N2O, CO and CO2 of the remote sensor IASI.
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This paper presents a novel model, based on neural network techniques, to produce short-term and locally specific forecasts of significant instability for flights in the terminal area of Rio de Janeiro's airport, Brazil. Twelve years of data were used for neural network training/validation and test. The test showed that the proposed model can grab the physical content inside the data set, and its performance is encouraging for the first and second hours to nowcast significant instability events.
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The multifrequency range imaging (RIM) capability of the Chung–Li VHF atmospheric radar is widely evaluated with long-term collected data. Effective corrections of range/time delay and range-weighting function effect for the radar echoes are achieved to improve the performance of RIM. The radar demonstrates its first successful observation of double-layer structures as well as their temporal and spatial variations with time. RIM results with and without significant precipitation are also shown.
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This paper presents a method for determining global cloud cover by analyzing satellite data. Knowledge of cloud coverage is not only important for climate studies but also provides valuable information in the monitoring of atmospheric trace gases. The research presented here is embedded in an operational chain, which allows us to derive the cloud-cover information in near real time, i.e., only hours after sensing by the satellite.
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Optical equipment is usually not made for harsh environments. At our atmospheric observation site on Ascension Island, commercially available optical mirrors were destroyed within weeks after being installed outside. To be able to continue our observations, we had to develop rugged optical mirrors that are able to sustain sea salt spray, volcanic dust, and regular cleaning without loosing their reflectivity and without adverse effects on the retrieval quality.
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Using data from a new airborne Hyperspectral Thermal Emission Spectrometer (HyTES) instrument, we present a technique for the detection and wide-area mapping of emission plumes of methane and other atmospheric trace gas species over challenging and diverse environmental conditions with high spatial resolution, that permits direct attribution to sources in complex environments.
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Microwave links in commercial cellular communication networks hold a promise for areal rainfall monitoring and could complement rainfall estimates from ground-based weather radars, rain gauges, and satellites. It has been shown that country-wide rainfall maps can be derived from the signal attenuations of microwave links in such a network. Here we give a detailed description of the employed rainfall retrieval algorithm and the corresponding code, which is freely provided at GitHub.
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